In this research the effectiveness of sawdust SD and Sawdust coated polyaniline SD/PANI composite, which is one of the environmentally friendly materials, cheap and available in very large quantities were testing to remove the bromothymol blue BTB and malachite green oxalate MGox dyes as chemical contaminants for industrial bio-waste water using Batch Adsorption technique. The adsorbents surfaces were diagnosed by using Fourier Transmission Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and UV-visible Spectroscopy to measure the adsorption capacity. The particle size of SD and SD/PANI composite surfaces were measured by particle size analyzer and the results of surface area of SD (0.8164) and SD/PANI (2.7325) m2 /g. This was due to the addition of polyaniline that led to increase the surface area of the sawdust and thus to increase their efficiency in the removal of the dyes.The adsorption properties of both adsorbents in the removal of dyes include the study of several factors on the adsorption process, which are contact time, the quantity of adsorbent, pH and temperature. It was found that the maximum removal of BTB is 49% and 99% at 15 minute on the surface of each of SD and SD/PANI composite, respectively while the maximum removal of MGox dye at 20 minute is 88% and 20% on the surface of each of the SD and SD/PANI composite, respectively. The rate of removal of dyes increases with increasing the adsorption time until reaches to the equilibrium time. The obtained results represented that the appropriate weight to remove BTB is (0.015)g and the percentage removal reaches to (69% and 97%) for each of SD and SD/PANI composite respectively. On the other hand, the suitable weight to remove the MGox is (0.025)g and the percentage removal reaches to (84% and 18%) for each of SD and SD/PANI composite, respectively.By studying the pH (3, 5, 7, 9, 11) effect at different temperatures (298, 308, 318)K, it was found that the highest percentage removal of BTB on the surface of SD reaches to 81% when pH = 3 and on the surface of SD/PANI composite the maximum percentage removal of dye reaches to 98% at the original pH of dye (3.5-4), and found a higher percentage removal of MGox dye on the surface of SD reaches to 99% at pH = 5 and on the surface of SD/PANI composite the percentage removal does not exceed 30% at the original pH of dye (3.5-4).From the analysis of the results of adsorption both BTB and MGox dyes on surfaces each of SD and SD/PANI composite by using Langmuir, Freundlich and Dubinin-Radushkevich isotherms, the results showed that Freundlich isotherm model is best suited to represent the adsorption of BTB dye and Langmuir isotherm model to represent the adsorption of MGox dye.In addition, the thermodynamics parameters (ΔHo, ΔSo, ΔGo) represented that the percentage removal increase with increase the temperature which indicate that the adsorption is endothermic process. The negative values of ΔGo show that the process is spontaneous. Positive values of ΔHo indicate an endothermic process in nature and indicating that the process occurs is physical adsorption in the adsorption of BTB because the values of ΔHo less than 20.9 kJ / mol but the process is chemical adsorption in the adsorption of MGox because the values of ΔHo more than 20.9 kJ/mol. The positive values of ΔSo indicate an increase randomly system and from the negative values of ΔGo found that spontaneous interaction where increases with increasing temperatures. Adsorption Kinetic study was found to follow a pseudo-second order rate expression for BTB dye on the surface of SD and SD/PANI composite and for MGox dye on SD. On the other hand, the adsorption kinetic study was found to follow a pseudo-first order rate for MGox on SD/PANI composite.
